Supported catalyst and method of preparing the same

ABSTRACT

A method of preparing a supported catalyst includes dissolving a cation exchange polymer in alcohol to prepare a solution containing cation exchange polymer; mixing the cation exchange polymer containing solution with a catalytic metal precursor or a solution containing catalytic metal precursor; heating the mixture after adjusting its pH to a predetermined range; adding a reducing agent to the resultant and stirring the solution to reduce the catalytic metal precursor; mixing the resultant with a catalyst support; adding a precipitating agent to the resultant to form precipitates; and filtering and drying the precipitates. The method of preparing a supported catalyst can provide a highly dispersed supported catalyst containing catalytic metal particles with a reduced average size regardless of the type of catalyst support, which provides better catalytic activity than conventional catalysts at the same loading amount of catalytic metal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 11/334,472,filed on Jan. 19, 2006, now U.S. Pat. No. 7,867,940, which claim thebenefit of Korean Application No. 10-2005-0005540, filed Jan. 20, 2005,in the Korean Patent Office, the disclosures of which are incorporatedherein, by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the present invention relate to a supported catalyst and amethod of preparing the same, and more particularly, to a highlydispersed supported catalyst containing catalytic metal particles withsmaller particle sizes regardless of the type of catalyst support and amethod of preparing the same.

2. Description of the Related Art

Conventionally, a supported catalyst refers to a catalyst composed of acatalyst component and a porous catalyst support to which the catalystcomponent adheres. The porous catalyst support has many pores, and thusa very large surface area. Such a large surface area provides a place inwhich many catalyst components can be dispersed. The supported catalystis widely used to accelerate various reactions in various fields.

An example of the supported catalyst is a carbon supported metalcatalyst. The carbon supported metal catalyst includes porous carbonparticles as a catalyst support and catalytic metal particles as acatalyst component. The carbon supported metal catalyst is also widelyused to accelerate various reactions in various fields. An example ofthe carbon supported metal catalyst is a catalyst contained in anelectrode for a fuel cell. More particularly, a cathode and/or an anodeof a fuel cell such as a phosphoric acid fuel cell (PAFC), a protonexchange membrane fuel cell (PEMFC), or a direct methanol fuel cell(DMFC) contain the carbon supported metal catalyst which accelerates anelectrochemical oxidation of a fuel and/or an electrochemical reductionof oxygen. In this case, carbon particles act as a catalyst support andas an electron conductor. Pt, Pt/Ru alloy, etc. are generally used asthe catalytic metal particles.

A method of preparing an anode electrode catalyst by adding a noblemetal colloid solution and carbon to an aqueous polymer solution inwater at a high temperature in a pressured state is discussed inJapanese Patent Laid-Open Publication No. 2003-123775. In supportedcatalysts prepared according to the above-described method, as well asin other methods, as the loading amount of catalytic metal particlesincreases, the average size of catalytic metal particles supported alsogenerally increases. For the reason of this, the improvement ofcatalytic activity of a supported catalyst through control of theaverage size of catalytic metal particles and the loading amount ofcatalytic metal particles is limited.

Moreover, in supported catalysts prepared according to conventionalmethods, even though the loading amount of catalytic metal particles isreduced, it is difficult to reduce the average size of catalytic metalparticles, and thus sufficient dispersion is not obtained. Thus, atechnology of improving dispersion while reducing the average size ofcatalytic metal particles supported on a catalyst support in a loadingamount of catalytic metal particles more than or equal to theconventional loading amount of catalytic metal particles needs to bedeveloped.

SUMMARY OF THE INVENTION

Aspects of the present invention provide a method of preparing a highlydispersed supported catalyst containing catalytic metal particles withreduced particle sizes regardless of the type of catalyst support and asupported catalyst prepared using the same.

According to an aspect of the present invention, a method of preparing asupported catalyst includes: dissolving a cation exchange polymer in asolvent to prepare a solution containing a cation exchange polymer;mixing the solution containing the cation exchange polymer with acatalytic metal precursor or a solution containing the catalytic metalprecursor; heating the mixture after adjusting its pH to within apredetermined range; adding a reducing agent or a solution containingthe reducing agent to the resultant and stirring the solution to reducethe catalytic metal precursor; mixing the resultant with a catalystsupport; adding a precipitating agent to the resultant to formprecipitates; and filtering and drying the precipitates.

According to an aspect of the present invention, there is provided asupported catalyst prepared according to the above-described method.

According to an aspect of the present invention, in the supportedcatalyst, catalytic metal particles have an average particle size of 2to 5 nm.

According to an aspect of the present invention, a highly dispersedsupported catalyst is obtained using a catalytic metal particle colloidwith good dispersion and a cation exchange polymer regardless of thetype of catalyst support.

According to an aspect of the present invention, in the supportedcatalyst, the content of the cation exchange polymer is 1 to 10 parts byweight based on 100 parts by weight of the catalyst support.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects and advantages of the present inventionwill become more apparent and more readily appreciated by describing indetail exemplary embodiments thereof with reference to the accompanyingdrawings in which:

FIG. 1 is a diagram illustrating a process of preparing a supportedcatalyst according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a supported catalyst according to anembodiment of the present invention;

FIG. 3 is a schematic diagram of a fuel cell according to an embodimentof the present invention;

FIGS. 4 and 5 are TEM photographs of supported catalysts according toExample 1 of the present invention and Comparative Example 1;

FIG. 6 is an X-ray diffraction analysis spectrum of supported catalystsaccording to Example 1 of the present invention and Comparative Example1;

FIG. 7 is a graph illustrating the relationship between the cellpotential and the current density in direct methanol fuel cellsaccording to Example 8 of the present invention and Comparative Example2; and

FIG. 8 is a graph illustrating the relationship between the cellpotential and the current density in direct methanol fuel cellsaccording to Example 8 of the present invention and Reference Example 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described inmore detail in relation to the accompanying drawings and specificexamples, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below in order to explain thepresent invention by referring to the figures and examples withoutlimitation thereto.

FIG. 1 is a diagram illustrating a process of preparing a supportedcatalyst according to an embodiment of the present invention. Referringto FIG. 1, a cation exchange polymer is first added to a solvent toobtain a cation exchange polymer solution (operation 101). While notrequired in all aspects, the solvent may be water, alcohol, polyol, orother like solvents. Where the solvent is alcohol, examples of thealcohol include, but are not limited to, ethanol, methanol, butanol,isopropanol, etc. The content of the solvent is adjusted to be 0.1 to 1mg of the cation exchange polymer per 1 ml of the cation exchangepolymer solution.

NAFION®, a polymer having a sulfonyl group or a phosphoryl group, or thelike is used as the cation exchange polymer according to an aspect ofthe invention. Examples of such a polymer include sulfonated polyimide,sulfonated polyetherketone, sulfonated polystyrene, sulfonatedpolysulfone and a mixture thereof. NAFION® refers to a perfluorocarbonsulfonic acid cation exchange resin. In addition, polysulfone,perfluorocarboxylic acid, styrene-vinyl benzene sulfonic acid, and otherlike polymers may be used as the cation exchange polymer.

In operation 102, a catalytic metal precursor or a catalytic metalprecursor solution is added to the solution containing cation exchangepolymer, and then mixed. According to an aspect of the invention, thecatalyst metal precursor is a precursor containing one or more metalsselected from the group consisting of Pt, Ru, Pd, Rh, Ir, Os, Au, ormixtures thereof. H₂PtCl₄, H₂PtCl₆, K₂PtCl₄, H₂PtCl₆ or a mixturethereof is used as a Pt precursor according to an aspect of theinvention. RuCl₃, (NH₄)₂[RuCl₆], or (NH₄)₂[RuCl₅H₂O] is used as a Ruprecursor according to an aspect of the invention H₂[AuCl₄],(NH₄)₂[AuCl₄], or H[Au(NO₃)₄]H₂O is used as a Au precursor according toan aspect of the invention. In the case of an alloy catalyst, a mixtureof metal precursors having a mixing ratio corresponding to a desiredmetal atomic ratio is used. However, it is understood that otherprecursors can be used or developed for the Pt, Ru and/or Au.

In an embodiment of the present invention, the content of the cationexchange polymer is 4 to 40 parts by weight based on 100 parts by weightof the catalytic metal precursor. If the content of the cation exchangepolymer is less than 4 parts by weight, agglomeration occurs in asolution when metal particles are formed, and thus sizes of catalyticmetal particles may increase. If the content of the cation exchangepolymer is greater than 40 parts by weight, metal particles have highlyhydrophobic surfaces, and thus are not uniformly supported on carbon.

The catalytic metal precursor solution is prepared by mixing thecatalytic metal precursor with a solvent. Examples of the solventsinclude, but are not limited to, water, alcohol, ethylene glycol, orother like solvents according to an aspect of the invention. The contentof the catalytic metal precursor in the catalytic metal precursorsolution is preferably 0.1 to 100 mg/ml. If the content of the catalyticmetal precursor is greater than 100 mg/ml, metal particles precipitatedue to instability. If the content of the catalytic metal precursor isless than 0.1 mg/ml, reduced metal particles may not adhere to carbon,and thus, it is not preferable. However, it is understood that othercontents may be used or developed according to the material used.

The pH of the obtained mixture is adjusted to 7-12 (in particular, toabout 8) in operation 103. The pH of the mixture is adjusted inoperation 103 to a predetermined range using a base, such as a NaOHaqueous solution according to an aspects of the invention.

In operation 104, the pH adjusted mixture is heated to 70 to 90° C. Atthe same temperature, a reducing agent or a solution containing reducingagent is added to the mixture (operation 105) and the mixture is stirredto reduce metal ions of the catalytic metal precursor to catalytic metalparticles. If the heating temperature is less than 70° C., an effect offacilitating reduction is trivial. If the heating temperature is greaterthan 90° C., it is difficult to expect uniform reduction due to toorapid reduction and sizes of catalytic metal particles increase.

The reducing agent added in operation 105 reduces the catalytic metalprecursor to a corresponding catalytic metal. Examples of the reducingagent include, but are not limited to, formaldehyde, formic acid,polyol, hydrazine, sodium borohydride, hydrogen gas, etc. Examples ofpolyol include, but are not limited to, ethylene glycol, glycerol,diethylene glycol, triethylene glycol, etc.

While not required in all aspects, when a solution containing thereducing agent is used, a solvent mixed with the reducing agent may bethe same as used when preparing the solution containing catalytic metalprecursor. The content of the reducing agent is 5 to 50 moles based on 1mole of the catalytic metal precursor. The content of the reducing agentin the solution containing reducing agent is preferably 2 to 10 parts byweight based on 100 parts by weight of the solution containing reducingagent.

Then, the resultant is cooled to room temperature (25° C.). A catalystsupport is added thereto (operation 106). Subsequently, a precipitatingagent is added in operation 107 and the result is stirred for apredetermined time. The catalyst support is not particularly restricted.Examples include Vulcan, Ketjen black, acetylene black, activated carbonpowder, carbon molecular sieve, carbon nanotube, activated carbon havingmicropores, mesoporous carbon or combinations thereof. The content ofthe catalyst support is 65 to 400 parts by weight based on 100 parts byweight of the metallic catalyst according to an aspect of the invention.If the content of the catalyst support is less than 65 parts by weight,sizes of the catalytic metal particles may increase. If the content ofthe catalyst support is greater than 400 parts by weight, the loadingamount is not sufficient to be used as a fuel cell catalyst.

While not required in all aspects, an acidic solution is used as theprecipitating agent in operation 107. Examples of the acidic solutioninclude, but are not limited to, an HCl solution, NaNO₃, an NaClsolution, or other like solutions. According to an aspect of theinvention, the HCl solution is used and a concentration of the HClsolution is 1 to 3 M. Preferably, the amount of the precipitating agentused is so large as to make the pH of the whole solution 3 or less.

Precipitates are formed by stirring, and then filtered and washed withexcessive deionized water. The obtained powder is dried to form asupported catalyst. The drying is performed at 50 to 100° C. In thesupported catalyst, catalytic metal particles with an average particlesize of 2 to 5 nm are uniformly distributed on the catalyst support.Thus, further improved catalytic activity can be obtained.

As discussed herein, the average particle size implies an averageparticle diameter when catalytic metal particles have a spherical form.In the supported catalyst of the present embodiment, if the averageparticle size of the catalytic metal particles is out of the aboverange, it is not preferable in terms of catalytic activity. Thesupported catalyst of the present embodiment is a highly dispersedsupported catalyst. As discussed herein, the term “highly dispersed”implies that an average particle size of catalytic metal particlessupported on a porous catalyst support is very small compared to aconventional supported catalyst and the catalytic metal particles areuniformly dispersed on carbon without agglomeration.

Referring to FIG. 2, the highly dispersed supported catalyst 10 of thepresent embodiment includes a porous catalyst support 11, catalyticmetal particles 12 adsorbed to the catalyst support 11, and a cationexchange polymer (so called “ionomer”) 13. The cation exchange polymer13 is introduced before the catalytic metal particles 12 are reduced andis expected to prevent agglomeration of catalyst metal particles 12during reduction and to facilitate proton conduction when applied in afuel cell since the polymer 13 is present between the catalytic metalparticles 12.

The content of the cation exchange polymer 13 is 1 to 10 parts by weightbased on 100 parts by weight of a porous catalyst support 11. Thecontent of catalytic metal particles 12 is 20 to 61 parts by weightbased on 100 parts by weight of the catalyst support 11. However, otherweights can be used.

In the present embodiment, particles 12 adsorbed to the catalyst support11 are Pt, Ru, Pd, Rh, Ir, Os, Au, or combinations thereof.

The supported catalyst can be used in an electrode catalyst layer of afuel cell according to an aspect of the invention. In addition, thesupported catalyst is used or is usable as a catalyst for variouschemical reactions, such as hydrogenation, dehydrogenation, coupling,oxidation, isomerization, decarboxylation, hydrocracking, and/oralkylation, etc. However, uses other than in a fuel cell are possible.

A direct methanol fuel cell (DMFC) according to an embodiment of thepresent invention using the supported catalyst in the formation of acathode layer will now be described in more detail with reference toFIG. 3. However, it is understood that the invention is usable withother fuel cells such as PAFC and PEMFC. Referring to FIG. 3, the DMFCof the present embodiment includes an anode 32 to which a fuel issupplied, a cathode 30 to which an oxidant is supplied, and anelectrolyte membrane 40 interposed between the anode 32 and the cathode30. In general, the anode 32 includes an anode diffusion layer 22 and ananode catalyst layer 33. The cathode 30 includes a cathode diffusionlayer 34 and a cathode catalyst layer 31. The anode catalyst layerand/or the cathode catalyst layer are composed of the supported catalystdescribed above in relation to FIGS. 1 and 2.

A bipolar plate 50 includes a passage for supplying a fuel to the anode32 and acts as an electron conductor for transporting electrons producedin the anode 32 to an external circuit or an adjacent unit cell. Abipolar plate 50 includes a passage for supplying an oxidant to thecathode 30 and acts as an electron conductor for transporting electronssupplied from the external circuit or the adjacent unit cell to thecathode 30. In the shown DMFC, a methanol aqueous solution is generallyused as the fuel supplied to the anode 32 and air is generally used asthe oxidant supplied to the cathode 30.

The methanol aqueous solution transported to the anode catalyst layer 33through the anode diffusion layer 22 is decomposed into electrons,hydrogen ions, carbon dioxide, etc. Hydrogen ions migrate to the cathodecatalyst layer 31 through the electrolyte membrane 40, electrons migrateto the external circuit, and carbon dioxide is discharged. In thecathode catalyst layer 31, hydrogen ions transported through theelectrolyte membrane 40, electrons supplied from the external circuit,and oxygen in air transported through the cathode diffusion layer 32react to produce water.

In such a DMFC, the electrolyte membrane 40 acts as a hydrogen ionconductor, an electron insulator, a separator, etc. When the electrolytemembrane 40 acts as the separator, it prevents unreacted fuel from beingtransported to the cathode 30 or a unreacted oxidant from beingtransported to the anode 32. Cation exchange polymers, such asperfluorosulfonic acid-based polymer having fluorinated alkylene intheir backbone and sulfonic acid groups at the terminals of fluorinatedvinylether side chains (e.g. NAFION® by DuPont), are generally used asmaterials for the electrolyte membrane 30 of the DMFC. Such a DMFC canbe used for portable devices, such as portable computers, phones,personal digital assistants, portable media players, and/or likedevices.

Aspects of the present invention will be described in greater detailwith reference to the following examples. The following examples are forillustrative purposes and are not intended to limit the scope of theinvention.

EXAMPLE 1

10 ml of ethanol was placed in a 250 ml round bottom flask and 133 mg ofa 5 wt % NAFION® solution (available from DuPont) was added thereto.Then, 8.1 ml of hexachloroplatinic (IV) acid aqueous solution inethylene glycol (Pt content: 7.4 mg Pt/ml EG) was added, followed by theaddition of 4.5 ml sodium hydroxide (1M) solution until a pH of 8 hadbeen reached. After stirring for about 30 minutes, the mixture washeated to 80° C.

7 ml of a formaldehyde solution in alcohol (3.7 wt %) was added dropwiseand stirred, and then cooled to room temperature. 90 mg of Vulcan XC-72was added to the obtained mixture and homogeneously mixed by stirring.After adding 9.1 ml of a 1.5 M HCl aqueous solution as a precipitatingagent, the mixture was stirred for 6 hours, then filtered and washedwith deionized water. The resultant was dried in an oven at 70° C. toobtain 40 wt % Pt/C particles. An average particle size of the Pt/Cparticles measured through TEM analysis was about 2.5 to 3 nm (FIG. 4).

EXAMPLE 2

20 wt % Pt/C particles were obtained in the same manner as Example 1,except that 65.7 mg of the NAFION® solution, 4 ml of hexachloroplatinic(IV) acid solution in ethylene glycol (Pt content: 7.4 mg Pt/ml EG) and2.5 ml of the 1 M sodium hydroxide solution were used. An averageparticle size of the Pt/C particles measured through TEM analysis wasabout 2 nm.

EXAMPLE 3

20 wt %-10 wt % PtRu/C particles were obtained in the same manner asExample 1, except that 99 mg of the NAFION® solution was used, 4 ml ofhexachloroplatinic (IV) acid solution in ethylene glycol (Pt content:7.4 mg Pt/ml EG) and 2 ml of a RuCl₃ solution (Ru content: 7.4 ml Ru/mlEG) were simultaneously added, and 10 ml of the 1 M sodium hydroxidesolution were used. An average particle size of the PtRu/C particlesmeasured through TEM analysis was about 2 nm.

EXAMPLE 4

30 wt %-15 wt % of PtRu/C particles was obtained in the same manner asExample 3, except that 148 mg of the NAFION solution was used, 4 ml ofhexachloroplatinic (IV) acid solution in ethylene glycol (Pt content:7.4 mg Pt/ml EG) and 2 ml of a RuCl₃ solution (Ru content: 7.4 ml Ru/mlEG) were simultaneously added, and 10 ml of the 1 M sodium hydroxidesolution were used. An average particle size of the PtRu/C particlesmeasured through TEM analysis was about 2.5 nm.

Comparing the method of preparing PtRu/C in Examples 3 and 4 with themethod disclosed in Japanese Patent Laid-Open Publication No.2003-123775, while both methods prepare catalysts using a cationexchange polymer, catalytic metal particles prepared according toExamples 3 and 4 were much smaller than those of the cited referencesince reduction was performed at atmospheric pressure and a temperaturelower than 90° C. As mentioned above, if a reducing agent is added at atemperature higher than 90° C., catalyst particles become large due totoo rapid a reduction.

EXAMPLES 5-7

40 wt % Pt/C particles were obtained in the same manner as Example 1,except that Ketjen Black (KB, specific surface area: 800 m²/g),Multi-Wall Carbon Nanotube (MWCNT, specific surface area: 200 m²/g) andDenka black (DB, specific surface area: 67 m²/g) were used instead ofVulcan XC-72. Average particle sizes of the Pt/C particles measuredthrough XRD analysis were 2.4 nm for the KB support, 2.9 nm for theMWCNT support, and 2.3 nm for the DB support.

COMPARATIVE EXAMPLE 1

40 wt % Pt/C particles was obtained in the same manner as Example 1,except that the NAFION®solution was not used. An average particle sizeof the Pt/C particles measured through TEM analysis was about 7 nm (FIG.5).

Referring to FIGS. 4 and 5, it can be seen that the average particlesize of the supported catalyst particles according to Example 1 issmaller than that of the supported catalyst particles according toComparative Example 1.

For the supported catalysts according to Example 1 and ComparativeExample 1, an X-ray diffraction (XRD) analysis was performed and theresults are illustrated in FIG. 6. Referring to FIG. 6, an XRD (a)spectrum for Example 1 has broader peaks than an XRD (b) spectrum forComparative Example 1, indicating that the size of catalytic metalparticles of Example 1 is smaller than that of catalytic metal particlesof Comparative Example 1. That is, the cation exchange polymer preventsagglomeration between Pt particles, and thus small catalyst particlesare supported on the carbon support.

EXAMPLE 8 Fabrication of a Fuel Cell

The Pt/C catalyst prepared in Example 1 was used as a cathode catalystand a NAFION® 115 membrane (DuPont) was used as an electrolyte membraneof a single cell. 32 mg of 40 wt % Pt/C (Example 1), water, and 4 ml ofethanol were homogeneously mixed by ultrasonic and stirring. 70 mg of 5wt % NAFION® solution was added to the mixture and mixed for 30 minutesby ultrasonic to obtain a homogeneous catalyst layer formingcomposition.

Next, the composition was applied to a diffusion layer (area: 2.5×5 cm²)to obtain a cathode with a noble metal loading amount of 1 mg Pt/cm². 20wt %-10 wt % PtRu/C (Johnson Matthey Inc.) was applied to an anodediffusion layer (area: 2.5×5 cm²) to obtain an anode with a noble metalloading amount of 2 mg Pt/cm².

A NAFION® solution was sprayed on the cathode and the anode and driedsuch that a dry NAFION® loading amount on the cathode and the anode was1 mg/cm². The cathode and the anode were hot pressed on both sides ofthe electrolyte membrane at 130° C. for 2 minutes to form a single cell.In the single cell, the cathode operated at about 90° C. An active areaof the single cell was 4 cm², a 1M methanol solution was supplied to theanode at a flow rate of 1 ml/min, and oxygen was supplied to the cathodeat a pressure of 0.2 Mpa.

COMPARATIVE EXAMPLE 2 Fabrication of a Fuel Cell

A fuel cell was fabricated in the same manner as Example 8, except thatthe Pt/C catalyst of Comparative Example 1 substituted the Pt/C catalystof Example 1.

REFERENCE EXAMPLE 1

A fuel cell was fabricated in the same manner as Example 1, except thata 40 wt % Pt/C (Johnson Matthey Inc.) was used as a cathode catalyst anda 20 wt %-10 wt % PtRu/C was used as an anode catalyst.

For fuel cells obtained in Example 8 and Comparative Example 2, therelationship between the voltage and the current density wasinvestigated and the results are illustrated in FIG. 7. Referring toFIG. 7, it can be seen that the fuel cell of Example 8 (curve a) hasbetter cell efficiency than the fuel cell of Comparative Example 2(curve b).

For fuel cells obtained in Example 8 and Reference Example 1, therelationship between the voltage and the current density wasinvestigated and the results are illustrated in FIG. 8. It can be seenfrom FIG. 8 that a highly dispersed 40 wt % Pt/C can be synthesizedusing a cation exchange polymer and better cell efficiency than thecommercially available catalyst can be ensured.

The method of preparing a supported catalyst according to an embodimentof the present invention provides a highly dispersed supported catalystcontaining catalytic metal particles with a reduced average sizeregardless of the type of catalyst support. The highly dispersedsupported catalyst has better catalytic activity than other catalysts atthe same loading amount of catalytic metal due to a reduced average sizeof catalytic metal particles. Specifically, other methods includepreparing a well dispersed PtRu catalyst using Nafion stabilizedalcohol-reduction method as discussed in Loka Subramanyam Sarma, Tzu DaiLin, Yin-Wen Tsai, Jium Ming Chen and Bing Joe Hwang, J. Power Source,139, 44-54 (2005), or preparing an anode electrode catalyst by adding anoble metal colloid solution and carbon to an aqueous polymer solutionin water at a high temperature in a pressured state is discussed inJapanese Patent Laid-Open Publication No. 2003-123775 result in anincrease of the average size of the catalytic metal particles supportedas the loading amount of catalytic metal particles increases. Thus, inthese other methods, the improvement of catalytic activity of asupported catalyst through control of the average size of catalyticmetal particles and the loading amount of catalytic metal particles islimited as compared to the sizes and loading amounts produced throughaspects of the invention.

While aspects of the present invention have been particularly shown anddescribed with reference to exemplary embodiments thereof, it will beunderstood by those of ordinary skill in the art that various changes inform and details may be made therein without departing from the spiritand scope of the present invention as defined by the following claimsand equivalents thereof.

1. A supported catalyst prepared by: dissolving a cation exchangepolymer in a solvent, to prepare a solution containing the cationexchange polymer; mixing the solution with a catalytic metal precursoror a solution containing the catalytic metal precursor, to produce amixture; heating the mixture greater than 70° C. and less than 90° C.,after adjusting a pH of the mixture to about 8 or higher, using a base,to obtain a resultant; adding a reducing agent to the resultant andstirring to reduce the catalytic metal precursor, to obtain anotherresultant; mixing the another resultant with a porous catalyst support;adding a precipitating agent to the mixed another resultant, to formprecipitates; and filtering and drying the precipitates, to prepare thesupported catalyst, wherein the supported catalyst includes the porouscatalyst support, catalytic metal particles adsorbed to the catalystsupport, and the cation exchange polymer, and the content of the cationexchange polymer is 1 to 10 parts by weight based on the 100 parts byweight of the porous catalyst support, and wherein the average particlesize of catalytic metal particles included in the supported catalyst isfrom 2 nm to 5 nm.
 2. The supported catalyst of claim 1, wherein thecation exchange polymer is at least one selected from the groupconsisting of a perfluorocarbon sulfonic acid cation exchange resin, asulfonated polyimide, a sulfonated polyetherketone, a sulfonatedpolystyrene, a sulfonated polysulfone, and a mixture thereof.
 3. Thesupported catalyst of claim 2, wherein the content of catalytic metalparticles is 20 to 61 parts by weight based on 100 parts by weight ofthe porous catalyst support.
 4. The supported catalyst of claim 1,wherein the content of the cation exchange polymer is from 4 to 10 partsby weight, based on 100 parts by weight of the catalytic metalprecursor.
 5. The supported catalyst of claim 1, wherein the reducingagent is at least one selected from the group consisting offormaldehyde, formic acid, polyol, hydrazine, sodium borohydride,hydrogen gas, and a mixture thereof.
 6. The supported catalyst of claim1, wherein the precipitating agent is an acidic solution.
 7. Thesupported catalyst of claim 1, wherein the catalytic metal precursor isat least one selected from the group consisting of H₂PtCl₄, H₂PtCl₆,K₂PtCl₄, (NH₄)₂[RuCl₆], (NH₄)₂[RuCl₅H₂O], H₂[AuCl₄], (NH₄)₂[AuCl₄],H[Au(NO₃)₄]H₂O, RuCl₃, and a combination thereof.
 8. The supportedcatalyst of claim 1, wherein the content of the catalytic metalprecursor included in the catalytic metal precursor containing solutionis from 0.1 to 100 mg/ml.
 9. The supported catalyst of claim 1, whereinthe catalyst support is at least one selected from the group consistingof Vulcan, Ketjen black, acetylene black, an activated carbon powder, acarbon molecular sieve, carbon nanotubes, an activated carbon havingmicropores, a mesoporous carbon, and a mixture thereof.
 10. An electrodeof a fuel cell, comprising the supported catalyst of claim
 1. 11. Thesupported catalyst of claim 1, wherein the solvent is at least oneselected from the group consisting of polyol, alcohol, water, and acombination thereof.
 12. The supported catalyst of claim 1, wherein theaverage particle size of catalytic metal particles included in thesupported catalyst is from 2.5 nm to 3 nm.